Abstract 18982: E3317 Promotes Cholesterol Efflux in Macrophage Cells via Enhancing ABCA1 Expression

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Introduction: Reverse cholesterol transport (RCT) is a process which plays an important role in cholesterol, lipid and glucose metabolism. Regulating the activities of key transporters and receptors within RCT, such as ATP-binding cassette transporter A1 (ABCA1), is beneficial to prevent diabetes and atherosclerotic related cardiovascular disease (CVD) in the various cells related to energy metabolism. However, the pharmacological and molecular regulators for ABCA1 are scarce. Here, we report that using an ABCA1 promoter luciferase reporter assay to screen ABCA1 activators, we have identified E3317 as an ABCA1 activator among 20000 compounds screened. E3317 could significantly up-regulate ABCA1 activity at a maximum value of 188% and the EC50 values of E3317 in ABCA1p-LUC HepG2 cells was 0.27 μmol·L–1.

Hypothesis: We hypothesized that E3317 might have anti-atherosclerotic effects and regulating cholesterol and lipid metabolism effects through upregulation of ABCA1.

Methods and Results: Our data showed that E3317 significantly increased ABCA1 mRNA and protein expression in both macrophages RAW264.7 and hepatic L02 cells. Mechanistic studies indicated that E3317 activated ABCA1 activity via activating nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ), which plays an important role in the regulation of glucose homeostasis and lipid metabolism. A site mutation assay confirmed that the key PPARγ binding epitopes of E3317 were Y327, F363, G284 and R288. Functionally, E3317 significantly decreased lipids accumulations in Oxidized low density lipoprotein (Ox-LDL) induced macrophages RAW264.7 and obviously increased cholesterol efflux to HDL in RAW264.7 cells. Further studies showed that the cholesterol efflux effect of E3317 is dependent on ABCA1 using ABCA1 siRNA. Our results have revealed that E3317 is an ABCA1 activator and E3317 promoted cholesterol efflux through upregulation of ABCA1.

Conclusions: Taken together, our findings first provide a novel beneficial cardiovascular effects and mechanism for compound E3317 and suggest that ABCA1 could be a novel pharmacological target for modulating endothelial function and combating atherosclerotic vascular disease.

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